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|
//! Dissolve internals
use std::{
iter::Extend,
convert::TryFrom,
};
use proc_macro2::{TokenStream, Span};
use quote::quote;
use syn::{
DeriveInput,
FieldsNamed,
Type,
Ident,
Result,
Error,
TypeTuple,
AttrStyle,
LitStr,
Attribute,
token::Paren,
punctuated::Punctuated,
parse::{Parse, ParseStream},
};
use crate::{
extract::{named_fields, named_struct},
faultmsg::Problem,
};
pub struct Field {
ty: Type,
name: Ident,
}
impl Field {
fn from_field(field: &syn::Field) -> Result<Self> {
let name: Ident = field.ident
.clone()
.ok_or(Error::new(Span::call_site(), Problem::UnnamedField))?;
Ok(Field {
ty: field.ty.clone(),
name: name,
})
}
fn from_fields_named(fields_named: &FieldsNamed) -> Result<Vec<Self>> {
fields_named.named
.iter()
.map(|field| Field::from_field(field))
.collect()
}
}
struct Rename {
name: Ident,
}
impl Parse for Rename {
fn parse(input: ParseStream) -> Result<Self> {
syn::custom_keyword!(rename);
if input.peek(rename) {
let _ = input.parse::<rename>()?;
let _ = input.parse::<syn::Token![=]>()?;
let name = input.parse::<LitStr>()?;
if !input.is_empty() {
Err(Error::new(Span::call_site(), Problem::TokensFollowNewName))
} else {
let name = Ident::new(name.value().as_str(), Span::call_site());
Ok(Rename { name } )
}
} else {
Err(Error::new(Span::call_site(), Problem::InvalidAttribute))
}
}
}
fn dissolve_rename_from(attributes: &[Attribute]) -> Result<Option<Ident>> {
let mut current: Option<Ident> = None;
for attr in attributes {
if attr.style != AttrStyle::Outer { continue; }
if attr.path.is_ident("dissolve") {
let rename = attr.parse_args::<Rename>()?;
current = Some(rename.name);
}
}
Ok(current)
}
pub struct NamedStruct<'a> {
original: &'a DeriveInput,
name: Ident,
fields: Vec<Field>,
dissolve_rename: Option<Ident>,
}
impl<'a> NamedStruct<'a> {
pub fn emit(&self) -> TokenStream {
let (impl_generics, struct_generics, where_clause) = self.original.generics
.split_for_impl();
let struct_name = &self.name;
let types: Punctuated<Type, syn::Token![,]> = self.fields
.iter()
.fold(Punctuated::new(), |mut p, field| {
p.push(field.ty.clone());
p
});
let type_tuple = TypeTuple {
paren_token: Paren { span: Span::call_site() },
elems: types,
};
let fields: TokenStream = self.fields
.iter()
.enumerate()
.fold(TokenStream::new(), |mut ts, (count, field)| {
if count > 0 {
ts.extend(quote!(,))
}
let field_name = &field.name;
let field_expr = quote!(
self.#field_name
);
ts.extend(field_expr);
ts
});
let dissolve = Ident::new("dissolve", Span::call_site());
let fn_name = self.dissolve_rename
.as_ref()
.unwrap_or(&dissolve);
quote!(
impl #impl_generics #struct_name #struct_generics
#where_clause
{
pub fn #fn_name(self) -> #type_tuple {
(
#fields
)
}
}
)
}
}
impl<'a> TryFrom<&'a DeriveInput> for NamedStruct<'a> {
type Error = Error;
fn try_from(node: &'a DeriveInput) -> Result<Self> {
let struct_data = named_struct(node)?;
let named_fields = named_fields(struct_data)?;
let fields = Field::from_fields_named(named_fields)?;
let rename = dissolve_rename_from(node.attrs.as_slice())?;
Ok(NamedStruct {
original: node,
name: node.ident.clone(),
fields,
dissolve_rename: rename,
})
}
}
|
